Molecular Variation in the Paragonimus heterotremus Complex in Thailand and Myanmar

Paragonimiasis is an important food-borne parasitic zoonosis caused by infection with lung flukes of the genus Paragonimus. Of the 7 members of the genus known in Thailand until recently, only P. heterotremus has been confirmed as causing human disease. An 8th species, P. pseudoheterotremus, has recently been proposed from Thailand, and has been found in humans. Molecular data place this species as a sister species to P. heterotremus, and it is likely that P. pseudoheterotremus is not specifically distinct from P. heterotremus. In this study, we collected metacercariae of both nominal species (identification based on metacercarial morphology) from freshwater crabs from Phetchabun Province in northern Thailand, Saraburi Province in central Thailand, and Surat Thani Province in southern Thailand. In addition, we purchased freshwater crabs imported from Myanmar at Myawaddy Province, western Thailand, close to the Myanmar-Thailand border. The DNAs extracted from excysted metacercariae were PCR-amplified and sequenced for ITS2 and cox1 genes. The ITS2 sequences were nearly identical among all samples (99-100%). Phylogenies inferred from all available partial cox1 sequences contained several clusters. Sequences from Indian P. heterotremus formed a sister group to sequences from P. pseudoheterotremus-type metacercariae. Sequences of P. heterotremus from Thailand, Vietnam, and China formed a separate distinct clade. One metacercaria from Phitsanulok Province was distinct from all others. There is clearly considerable genetic variation in the P. heterotremus complex in Thailand and the form referred to as P. pseudoheterotremus is widely distributed in Thailand and the Thai-Myanmar border region.

Paragonimus worm from a New Guinea native in 1926

OBJECTIVE@#To reobserve and research the specimen of Paragonimus worm found in the left lung of a New Guinea native in 1926, which was previously identified as Paragonimus westermani Kerbert or Paragonimus ringeri Cobbold.@*METHODS@#Using reconstructive software and microscopy to observe some organs of the worm, and compared with other species of paragonimus.@*RESULTS@#The three dimensional (3D) views of ovary and two testes of New Guinea specimen showed that the ovary was clearly divided into six lobes. These two testes were situated oppositely in the body. One teste was divided into four branches, while another was divided into five. The cuticular spines were arranged in groups over the entire skin covered in a slide, each group was consisted of two to four single spine.@*CONCLUSIONS@#Based on 3D views and measurements, we reclassified it as Paragonimus siamensis. This was also the first report of human case infected by Paragonimus siamensis.

Codon usage and bias in mitochondrial genomes of parasitic platyhelminthes

Sequences of the complete protein-coding portions of the mitochondrial (mt) genome were analysed for 6 species of cestodes (including hydatid tapeworms and the pork tapeworm) and 5 species of trematodes (blood flukes and liver- and lung-flukes). A near-complete sequence was also available for an additional trematode (the blood fluke Schistosoma malayensis). All of these parasites belong to a large flatworm taxon named the Neodermata. Considerable variation was found in the base composition of the protein-coding genes among these neodermatans. This variation was reflected in statistically-significant differences in numbers of each inferred amino acid between many pairs of species. Both convergence and divergence in nucleotide, and hence amino acid, composition was noted among groups within the Neodermata. Considerable variation in skew (unequal representation of complementary bases on the same strand) was found among the species studied. A pattern is thus emerging of diversity in the mt genome in neodermatans that may cast light on evolution of mt genomes generally.

DNA sequences of Paragonimus skrjabini populations from five provinces in China / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>To study differences among Paragonimus skrjabini (P. skrjabini) populations from five provinces in China (Guangdong, Fujian, Yunnan, Hubei, and Sichuan) and Paragonimus szechuanensis.</p><p><b>METHODS</b>DNA sequences were obtained from the ITS2 and CO1 genes and phylogenetic trees were constructed from the results. Sequences were also obtained from several other species of Paragonimus for comparative purposes.</p><p><b>RESULTS</b>Although differences existed in the DNA sequence among P. skrjabini populations from five provinces, the differences were very small. There was also some resemblance between P. miyazakii from Japan and Fujian strains of P. skrjabini.</p><p><b>CONCLUSION</b>All studied populations can be regarded as different strains of P. skrjabini; P. szechuanensis is not a separate species but may be a geographical strain of P. skrjabini. We also found that P. miyazakii may be synonymous with P. skrjabini.</p>